Source parameters and aftershock pattern of the October 7,2021,M5.9 Harnai earthquake,Pakistan

On October 7,2021,a magnitude 5.9 earthquake struck the Harnai(Baluchistan)region of Pakistan,causing several fatalities and injuries within the epicentral area.First-order tectonic deformation in this region is caused by the convergence of the Indian Plate with respect to the Eurasian Plate.The Katwaz Block hinders the motion of the Indian Plate,resulting in the formation of strike-slip faults.In this study,the P-wave first-motion polarity technique was used to determine the mainshock faulting style.Cyclic scanning of the polarity solutions was applied to determine the most suitable focal mechanism solution among the available solutions generated by the FOCMEC(focal mechanism)software.The nodal planes correspond to different faulting styles(i.e.,thrust and strike-slip faulting).A nodal plane oriented in the NW-SE direction corresponded to a strike-slip mechanism,which was considered to be the fault plane.Tectonically,this earthquake was associated with the Harnai-Karahi strike-slip fault zone owing to the fault strike and direction of slip.The apparent stress drop,fault length,and moment magnitude of the Harnai earthquake were 35.4 bar,6.1 km,and 5.9,respectively.A lower b-value for the Gutenberg-Richter law was observed prior to the earthquake.Higherα-than b-values(α>b)indicate that this earthquake was governed by large events as opposed to small-magnitude events.The Harnai sequence had a decay exponent close to unity,lasted for 145 days,and produced few aftershocks.The study will help the future hazard mitigation in the region.

Analysis and key control technologies to prevent spontaneous coal combustion occurring at a fully mechanized caving face with large obliquity in deep mines

In order to prevent spontaneous coal combustion occurring at a fully mechanized caving face with large obliquity in deep mines in China, we have analyzed the characteristics of spontaneous coal combustion and explain theoretically the factors affecting spontaneous coal combustion, such as rock bursts, high temperatures, high ventilation resistance, slow advancing speed and large obliquity mining. Key technologies to prevent spontaneous combustion occurring in sharply inclined seams in deep mines are pro- posed; these include pouring water, stopping leakage in upper and lower comers of the working face, choking off the goaf and cov- eting the coal. CO concentrations were controlled within two years to less than 15×10^-6 at the upper comer by applying these tech- nologies at the 1410 working face of the Huafeng coal mine. Our method has significant theoretical value and is of practical impor- tance in controlling spontaneous coal combustion occurring at a fully mechanized caving face with large obliquity in deep mines.